Circulating Monocyte Subsets Research Articles

Circulating intermediate CD14++CD16+monocytes are increased in patients with atrial fibrillation and reflect the functional remodelling of the left atrium.

A recent large clinical study demonstrated the association between intermediate CD14++CD16+monocytes and cardiovascular events. However, whether that monocyte subset contributes to the pathogenesis of atrial fibrillation (AF) has not been clarified. We compared the circulating monocyte subsets in AF patients and healthy people, and investigated the possible role of intermediate CD14++CD16+monocytes in the pathophysiology of AF. This case-control study included 44 consecutive AF patients without systemic diseases referred for catheter ablation at our hospital, and 40 healthy controls. Patients with systemic diseases, including structural heart disease, hepatic or renal dysfunction, collagen disease, malignancy, and inflammation were excluded. Monocyte subset analyses were performed (three distinct human monocyte subsets: classical CD14++CD16-, intermediate CD14++CD16+, and non-classical CD14+CD16++monocytes). We compared the monocyte subsets and evaluated the correlation with other clinical findings. A total of 60 participants (30 AF patients and 30 controls as an age-matched group) were included after excluding 14 AF patients due to inflammation. Atrial fibrillation patients had a higher proportion of circulating intermediate CD14++CD16+monocytes than the controls (17.0 ± 9.6 vs. 7.5 ± 4.1%, P < 0.001). A multivariable logistic regression analysis demonstrated that only the proportion of intermediate CD14++CD16+monocytes (odds ratio: 1.316; 95% confidence interval: 1.095-1.582, P = 0.003) was independently associated with the presence of AF. Intermediate CD14++CD16+monocytes were negatively correlated with the left atrial appendage flow during sinus rhythm (r= -0.679, P = 0.003) and positively with the brain natriuretic peptide (r = 0.439, P = 0.015). Intermediate CD14++CD16+monocytes might be closely related to the pathogenesis of AF and reflect functional remodelling of the left atrium.

Abstract 11695: The Kinetics of Circulating Monocyte Subsets and Microbial Translocation in the Acute Phase of ST-Elevation Myocardial Infarction Reveals Prognostic Values for Cardiovascular Outcomes

Introduction: In experimental myocardial infarction (MI), a rise in cell counts of circulating monocyte subsets contributes to impaired myocardial healing, and to atherosclerotic plaque destabilization.The underlying pathophysiological mechanisms for the post-MI monocytosis and the prognostic role of monocyte subsets in patients suffering ST-elevation MI (STEMI) are still unclear. Hypothesis: The kinetics of the three monocyte subsets (classical CD14++CD16-, intermediate CD14++CD16+ and non-classical CD14+CD16++ monocytes) and gut microbial translocation are associated with cardiovascular outcomes after STEMI. Methods: In 100 STEMI patients treated with primary percutaneous coronary intervention (PCI), monocyte subsets and microbial translocation markers (lipopolysaccharide [LPS] and D-lactate) were measured on Days 1, 2, 3, 5 and 7 of STEMI onset, compared with 35 stable coronary heart disease patients and 35 healthy volunteers. All STEMI patients were prospectively followed for the first occurrence of an adverse cardiovascular event. Results: From Day 1 to Day 7, a parallel increase in CD14++CD16- cell counts, CD14++CD16+ cell counts, and gut permeability markers was observed, with peak levels on Day 2. During a median follow-up of 1.5 years, 25 events were recorded. Univariate Kaplan-Meier analysis revealed that Day 2 CD14++CD16- cell counts ( P =0.022), CD14++CD16+ cell counts ( P =0.024) and Δ LPS (Day 2 – Day 1; P =0.027) each predicted the primary endpoint when stratified by median values. After adjustment for confounders, Day 2 CD14++CD16+ monocyte counts showed the strongest predictive value (per SD increase: hazard ratio [HR]: 2.127; 95% CI 1.313 to 3.446; P =0.002) for cardiovascular events. Conclusions: The expansion of the CD14++CD16+ monocyte subset on Day 2, which is associated a transient increase in microbial translocation, independently predicts adverse cardiovascular outcome in STEMI patients treated with primary PCI.

Abstract 15497: Hematopoietic PI3-Kinase delta-Deficiency Causes Altered Macrophage and Regulatory T-cell Function and Aggravates Atherosclerosis in LDLR-/- Mice

Atherosclerosis and its consequences such as myocardial infarction and ischemic stroke remains the leading cause of death in western countries. During atherogenesis, arterial blood vessels become infiltrated by macrophages and T cells possessing inflammatory and regulatory functions. Leukocytes express the catalytic phosphoinositide 3-kinase isoform p110d (PI3Kd), exerting a key role in the regulation of immune responses including activation, differentiation and effector function. Therefore, PI3Kd represents a promising target for the modulation of inflammatory processes during atherogenesis. To investigate the role of leukocytic PI3Kd during atherogenesis, lethally irradiated LDLR-/- mice were transplanted with bone marrow from PI3Kd-/- or PI3Kd+/+ mice and were fed an atherogenic diet for 6 weeks. Hypercholesterolemic PI3Kd-/- recipient LDLR-/- mice displayed a profound reduction of peripheral B and T cells as well as strongly impaired CD4+ T-cell activation, T-helper 1 response and regulatory T-cell numbers in paraaortic lymph nodes and spleen compared with PI3Kd+/+ transplanted controls. Surprisingly, the profoundly impaired PI3Kd-deficient immune system caused a substantial aggravation of atherosclerosis in LDLR-/- mice. Atherosclerotic lesion area at the aortic root and whole aorta of PI3Kd-/- recipient LDLR-/- mice was significantly increased by 72% and 218% compared with PI3Kd+/+ recipients, respectively (n = 10-20; P &lt; 0.001). Importantly, atherosclerotic lesions of PI3Kd-/- transplanted LDLR-/- mice were characterized by a lower fraction of CD4+ T cells and a higher proportion of macrophages compared with controls despite unaltered circulating monocyte subsets. Moreover, PI3Kd-deficient regulatory T cells and macrophages exhibited a strongly impaired suppressive capacity and an increased inflammatory polarization, respectively. In summary, we demonstrate that hematopoietic PI3Kd plays a crucial role in regulating innate and adaptive immune responses within the arterial wall by exerting protective functions during atherogenesis. Current studies aim to dissect PI3Kd-dependent mechanisms that modulate inflammatory and regulatory processes in multiple stages of atherosclerosis.

Elevated circulating CD14lowCD16+ monocyte subset in primary biliary cirrhosis correlates with liver injury and promotes Th1 polarization.

Primary biliary cirrhosis (PBC) is a progressive autoimmune liver disease in which monocytes/macrophages infiltration and skewed T helper type (Th) 1 and Th17 cell responses participate in the development of the disease. Human peripheral blood monocytes are heterogeneous and can be divided into classical CD14highCD16-, intermediate CD14highCD16+, and nonclassical CD14lowCD16+ monocyte subsets. Compared to classical monocytes, CD16+ monocytes are generally termed pro-inflammatory monocytes and play an important pathogenic role in autoimmune diseases. However, little is known about the immunophenotype and immunopathogenic role of peripheral blood CD16+ monocytes in PBC. Thus, we investigated the phenotype and function of these circulating monocyte subsets from PBC patients. The frequencies of circulating CD14highCD16+ and CD14lowCD16+ subpopulation were increased in disease compared with healthy controls. Among them, CD14lowCD16+ monocyte subset positively correlated with disease progress, liver damage indicators and serum C-reactive protein, respectively. Furthermore, the frequencies of Th1 and Th17 cells were upregulated and CD14lowCD16+ monocyte subset was also positively associated with Th1 cell frequency in PBC. Using a vitro coculture model, we further found that CD14lowCD16+ monocytes promoted Th1 cell polarization compared to classical monocytes. Interleukin-12 (IL-12) and direct contact of patient CD4+T cell and CD14lowCD16+ monocytes, were responsible for CD14lowCD16+ monocytes promotion of Th1 cells polarization in PBC. Our study demonstrated that the enhanced CD14lowCD16+ monocyte subset participated in fostering liver damage and inflammatory responses, and promoted Th1 cells skewing in PBC.

Surface APRIL Is Elevated on Myeloid Cells and Is Associated with Disease Activity in Patients with Rheumatoid Arthritis.

To assess surface APRIL (a proliferation-inducing ligand; CD256) expression by circulating myeloid cells in rheumatoid arthritis (RA) and to determine its relationship to disease activity. Peripheral blood mononuclear cells (PBMC) and plasma were obtained from patients with RA and healthy donors. PBMC were stained for flow cytometry to detect surface APRIL and blood cell markers to identify circulating myeloid cell subsets. Based on CD14 and CD16 phenotypes, monocyte subsets described as classical (CD14+CD16-), intermediate (CD14+CD16+), and nonclassical (CD14loCD16+) were identified. Levels of surface APRIL expression were measured by flow cytometry and median fluorescence intensity was used for comparisons. Levels of soluble APRIL in the plasma were determined by ELISA. Disease activity was measured by the Disease Activity Score in 28 joints. In patients with RA, total myeloid cells showed expression of surface APRIL that correlated with disease activity and with plasma APRIL levels observed in these patients. In healthy donors, classical monocytes were composed of > 80% of circulating monocytes. However, in patients with RA, the intermediate and nonclassical subsets were elevated and made up the majority of circulating monocytes. In contrast to healthy donors, where high levels of surface APRIL were only observed in nonclassical monocytes, patients with RA showed high levels of surface APRIL expression by all circulating monocyte subsets. Surface APRIL is elevated in circulating myeloid cells in patients with RA where it is highly correlated with disease activity. Patients with RA also showed skewing of monocytes toward subsets associated with secretion of tumor necrosis factor-α and/or interleukin 1β.

Abstract 15489: Hematopoietic PI3-Kinase δ-Deficiency Exacerbates Lesional Macrophage Infiltration and Atherosclerosis in LDLR-/- Mice

Atherosclerosis and its consequences such as myocardial infarction and ischemic stroke remains the leading cause of death in western countries. Atherosclerosis is a chronic inflammatory disease of arterial blood vessels, critically involving macrophages, dendritic cells and T lymphocytes. Leukocytes highly express the catalytic phosphoinositide 3-kinase isoform p110δ (PI3Kδ), exerting a key role in the regulation of immune responses including activation, differentiation and effector function of lymphocytes. Therefore, PI3Kδ represents a promising target for the modulation of inflammatory processes during atherogenesis. To investigate the role of leukocytic PI3Kδ during atherogenesis, lethally irradiated LDLR -/- mice were either transplanted with bone marrow from PI3Kδ -/- or PI3Kδ +/+ mice. After recovery, recipient mice were fed an atherogenic diet for 6 weeks. Hypercholesterolemic PI3Kδ -/- recipient LDLR -/- mice displayed a profound reduction of peripheral B and T cells as well as strongly impaired CD4 + T-cell activation, T-helper 1 response and regulatory T-cell numbers in paraaortic lymph nodes and spleen compared with PI3Kδ +/+ transplanted controls. Surprisingly, the profound impairment of the adaptive immune system by PI3Kδ-deficiency caused a considerable aggravation of atherosclerosis in LDLR -/- mice. Atherosclerotic lesion area at the aortic root and abdominal aorta of PI3Kδ -/- recipient LDLR -/- mice was significantly increased by 72% and 218% compared with PI3Kδ +/+ recipients, respectively (n = 10[[Unable to Display Character: &amp;#8211;]]20; P &lt; 0.001). Importantly, atherosclerotic lesions of PI3Kδ-deficient LDLR -/- mice were characterized by a lower fraction of CD4 + T cells and a higher proportion of MOMA-2 + monocytes/macrophages compared with controls despite unaltered circulating monocyte subsets. Thus, PI3Kδ-deficiency in mononuclear phagocytes may contribute to enhanced plaque growth. In summary, we demonstrate that hematopoietic PI3Kδ plays a crucial role in regulating innate and adaptive immune responses within the arterial wall by exerting protective functions during atherogenesis. Current studies aim to dissect PI3Kδ-dependent mechanisms that modulate inflammatory and regulatory processes in multiple stages of atherosclerosis.

Imbalance of circulating monocyte subsets and PD-1 dysregulation in Q fever endocarditis: the role of IL-10 in PD-1 modulation.

Q fever endocarditis, a severe complication of Q fever, is associated with a defective immune response, the mechanisms of which are poorly understood. We hypothesized that Q fever immune deficiency is related to altered distribution and activation of circulating monocyte subsets. Monocyte subsets were analyzed by flow cytometry in peripheral blood mononuclear cells from patients with Q fever endocarditis and controls. The proportion of classical monocytes (CD14+CD16− monocytes) was similar in patients and controls. In contrast, the patients with Q fever endocarditis exhibited a decrease in the non-classical and intermediate subsets of monocytes (CD16+ monocytes). The altered distribution of monocyte subsets in Q fever endocarditis was associated with changes in their activation profile. Indeed, the expression of HLA-DR, a canonical activation molecule, and PD-1, a co-inhibitory molecule, was increased in intermediate monocytes. This profile was not restricted to CD16+ monocytes because CD4+ T cells also overexpressed PD-1. The mechanism leading to the overexpression of PD-1 did not require the LPS from C. burnetii but involved interleukin-10, an immunosuppressive cytokine. Indeed, the incubation of control monocytes with interleukin-10 led to a higher expression of PD-1 and neutralizing interleukin-10 prevented C. burnetii-stimulated PD-1 expression. Taken together, these results show that the immune suppression of Q fever endocarditis involves a cross-talk between monocytes and CD4+ T cells expressing PD-1. The expression of PD-1 may be useful to assess chronic immune alterations in Q fever endocarditis.

Serial characterisation of monocyte and neutrophil function after lung resection

ObjectivesThe primary aim of this prospective study was to perform a comprehensive serial characterisation of monocyte and neutrophil function, circulating monocyte subsets, and bronchoalveolar lavage (BAL) fluid after lung resection....

Infliximab therapy increases the frequency of circulating CD16(+) monocytes and modifies macrophage cytokine response to bacterial infection.

Crohn's disease (CD) has been correlated with altered macrophage response to microorganisms. Considering the efficacy of infliximab treatment on CD remission, we investigated infliximab effects on circulating monocyte subsets and on macrophage cytokine response to bacteria. Human peripheral blood monocyte-derived macrophages were obtained from CD patients, treated or not with infliximab. Macrophages were infected with Escherichia coli, Enterococcus faecalis, Mycobacterium avium subsp. paratuberculosis (MAP) or M. avium subsp avium, and cytokine levels [tumour necrosis factor (TNF) and interleukin (IL)-10] were evaluated at different time-points. To evaluate infliximab-dependent effects on monocyte subsets, we studied CD14 and CD16 expression by peripheral blood monocytes before and after different infliximab administrations. We also investigated TNF secretion by macrophages obtained from CD16(+) and CD16(-) monocytes and the frequency of TNF(+) cells among CD16(+) and CD16(-) monocyte-derived macrophages from CD patients. Infliximab treatment resulted in elevated TNF and IL-10 macrophage response to bacteria. An infliximab-dependent increase in the frequency of circulating CD16(+) monocytes (particularly the CD14(++) CD16(+) subset) was also observed (before infliximab: 4·65 ± 0·58%; after three administrations: 10·68 ± 2·23%). In response to MAP infection, macrophages obtained from CD16(+) monocytes were higher TNF producers and CD16(+) macrophages from infliximab-treated CD patients showed increased frequency of TNF(+) cells. In conclusion, infliximab treatment increased the TNF production of CD macrophages in response to bacteria, which seemed to depend upon enrichment of CD16(+) circulating monocytes, particularly of the CD14(++) CD16(+) subset. Infliximab treatment of CD patients also resulted in increased macrophage IL-10 production in response to bacteria, suggesting an infliximab-induced shift to M2 macrophages.

Nitric oxide production by monocytes in children with OSA and endothelial dysfunction

OSA (obstructive sleep apnoea) is associated with a higher risk for alterations in post-occlusive hyperaemia, an eNOS (endothelial NO synthase)-dependent endothelial response. However, since not all children manifest endothelial dysfunction, we hypothesized that differences in circulating monocyte subsets and NO production may underlie the vascular phenotype in paediatric OSA. Matched pre-pubertal children with OSA with abnormal endothelial function (OSAab) and with normal endothelial function (OSAn), and controls (CO) were recruited. Peripheral blood mononuclear cells were subtyped into CD14+ and CD16+ cells, and NO production was assessed using flow cytometry. Endothelial dysfunction was defined as Tmax (time to reach maximal reperfusion)>45 s by laser Doppler flowmetry. A total of 11 OSAab, 12 OSAn and 12 CO-matched children completed the study. The OSAab group had increased CD16+ and decreased CD14+ cell numbers. They also had increased CX3CR1 (CX3C chemokine receptor 1) expression in CD16+ monocytes (P<0.01). Furthermore, monocytes from the OSAab group exhibited overall reduced NO production (787±71 compared with 1226±229 and 1089±116 median fluorescence intensity in the OSAn group and CO children respectively; P<0.01). Significant bivariate associations emerged between NO production, monocyte subsets, CX3CR1 in CD16+ monocytes, the CD14+/CD16+ ratio and Tmax. Thus OSA in children is associated with increased numbers of pro-inflammatory monocytes and reduced NO production in circulating monocytes that are closely associated with endothelial function.

Circulating CD14brightCD16+ 'intermediate' monocytes exhibit enhanced parasite pattern recognition in human helminth infection.

Circulating monocyte sub-sets have recently emerged as mediators of divergent immune functions during infectious disease but their role in helminth infection has not been investigated. In this study we evaluated whether ‘classical’ (CD14brightCD16−), ‘intermediate’ (CD14brightCD16+), and ‘non-classical’ (CD14dimCD16+) monocyte sub-sets from peripheral blood mononuclear cells varied in both abundance and ability to bind antigenic material amongst individuals living in a region of Northern Senegal which is co-endemic for Schistosoma mansoni and S. haematobium. Monocyte recognition of excretory/secretory (E/S) products released by skin-invasive cercariae, or eggs, of S. mansoni was assessed by flow cytometry and compared between S. mansoni mono-infected, S. mansoni and S. haematobium co-infected, and uninfected participants. Each of the three monocyte sub-sets in the different infection groups bound schistosome E/S material. However, ‘intermediate’ CD14brightCD16+ monocytes had a significantly enhanced ability to bind cercarial and egg E/S. Moreover, this elevation of ligand binding was particularly evident in co-infected participants. This is the first demonstration of modulated parasite pattern recognition in CD14brightCD16+ intermediate monocytes during helminth infection, which may have functional consequences for the ability of infected individuals to respond immunologically to infection.

High-salt intake induced visceral adipose tissue hypoxia and its association with circulating monocyte subsets in humans

To investigate the feasibility of blood oxygen level dependent magnetic resonance imaging (BOLD-MRI) in evaluating human visceral adipose tissue (AT) oxygenation induced by salt loading/depletion and its association with changes in circulating monocyte subsets. A dietary intervention study was performed in 23 healthy volunteers beginning with a 3-day usual diet followed by a 7-day high-salt diet (≥15 g NaCl/day) and a 7-day low-salt diet (≤5 g NaCl/day). BOLD-MRI was used to evaluate oxygenation in perirenal AT. Salt loading led to a consistent AT hypoxia (increase in the R2* signal, 25.2 ± 0.90 s(-1) vs. baseline 21.5 ± 0.71 s(-1) , P < 0.001) and suppression of circulating renin-angiotensin-aldosterone system (RAAS), as well as an expansion of the CD14++CD16+ monocytes and monocyte pro-inflammatory activation. In salt depletion phase, the hypoxic state of AT and the expanded CD14++CD16+ monocyte pool were regressed to baseline levels, accompanied by a rebound activation of RAAS. Moreover, AT oxygenation level was positively correlated with the CD14++CD16+ monocytes (r = 0.419, P < 0.001). This work provides proof-of-principle evidence supporting the feasibility of BOLD-MRI in monitoring visceral AT oxygenation in humans induced by dietary salt loading/depletion. In addition, the CD14++CD16+ monocytes may participate in the pathogenesis of high-salt intake induced AT hypoxia.

An unbalanced PD-L1/CD86 ratio in CD14++CD16+ monocytes is correlated with HCV viremia during chronic HCV infection

Circulating monocyte subsets with distinct functions play important roles in hepatitis C virus (HCV) infection. However, the mechanisms have not been well studied. In this study, we analyzed the distributions and phenotypic characteristics of three circulating monocyte subsets-CD14(++)CD16(-), CD14(++)CD16(+) and CD14(+/dim)CD16(+)-in chronic HCV-infected patients, HCV spontaneous resolvers and healthy controls, and we evaluated the possible link between HCV viremia and disease progression. Our results indicated that the frequency of the CD14(++)CD16(+) monocyte subset was decreased, and negatively correlated with HCV RNA and core antigen levels during chronic HCV infection. PD-L1 expression and the PD-L1/CD86 ratio in CD14(++)CD16(+) monocytes were higher during chronic HCV infection than in spontaneous HCV resolvers and healthy controls. The PD-L1/CD86 ratio positively correlated with HCV viral load and core antigen levels. Finally, PD-L1 was significantly increased, while cytokine secretions were dramatically decreased upon Toll-like receptor (TLR) ligand binding and HCV JFH-1stimulation. These findings indicates the compromised immune status of the CD14(++)CD16(+) monocytes during chronic HCV infection and provides new insights into the specific role of the CD14(++)CD16(+) monocytes and their significance in chronic HCV infection.

The Role of HIV and Monocytes/Macrophages in Adipose Tissue Biology

To assess the role of HIV and monocytes/macrophages in adipose tissue dysregulation. Cross-sectional study in 5 groups: HIV seronegative, HIV+ antiretroviral therapy (ART)-naive, HIV+ nonlipoatrophic on zidovudine- and/or stavudine-containing ART, HIV+ lipoatrophic on similar ART, and HIV+ on abacavir- or tenofovir-containing ART. HIV DNA in circulating monocyte subsets was quantitated by real-time polymerase chain reaction. Biopsied subcutaneous fat was examined for macrophage content by CD68 staining. Isolated adipocytes and macrophages were cultured and the supernatant assayed for secretory products by Luminex multiplex cytokine technology. Sixty-nine subjects were enrolled. Lipoatrophic subjects had higher median HIV DNA levels (270.5 copies/10 cells) in circulating peripheral CD14CD16 co-expressing monocyte subsets compared with subjects who were ART-naive (25.0 copies), nonlipoatrophic (15.0 copies), or on abacavir/tenofovir (57.5 copies), P < 0.01. Group differences in adipocytes and adipose macrophage content were marginal. Although adipocyte secretory products were similar, HIV-infected subjects had higher adipose macrophage-derived interleukin (IL)-12p40, IL-6, IL-8, and monocyte inflammatory protein 1 alpha and lower eotaxin and interferon gamma levels than HIV seronegative subjects (P < 0.05). Within HIV-infected subjects, adipose macrophage secretory products were comparable between subjects naive with ART versus those on ART. Circulating HIV-infected and proinflammatory CD14CD16 monocyte subsets contribute to the pathogenesis of HIV-associated lipoatrophy. Among HIV-infected individuals, macrophages, rather than adipocytes, are the primary source of low-grade inflammation in subcutaneous adipose tissue. HIV infection modifies these macrophages to a more proinflammatory phenotype, and these changes are not substantially mitigated by the use of ART.

Tissue LyC6− Macrophages Are Generated in the Absence of Circulating LyC6− Monocytes and Nur77 in a Model of Muscle Regeneration

There are several open questions regarding the origin, development, and differentiation of subpopulations of monocytes, macrophages (MFs), and dendritic cells. It is a particularly intriguing question how circulating monocyte subsets develop and contribute to the generation of steady-state and inflammatory tissue MF pools and which transcriptional mechanisms contribute to these processes. In this study, we took advantage of a genetic model in which LyC6(-) circulating monocyte development is severely diminished due to the lack of the nuclear receptor, NUR77. We show that, in a mouse model of skeletal muscle injury and regeneration, the accumulation of leukocytes and the generation of LyC6(+) and LyC6(-) MF pools are intact in the absence of circulating LyC6(-) blood monocytes. These data suggest that NUR77, which is required for LyC6(-) blood monocyte development, is expressed but not critically required for LyC6(+) to LyC6(-) tissue MF specification. Moreover, these observations support a model according to which tissue macrophage subtype specification is distinct from that of circulating monocytes. Lastly, our data show that in the used sterile inflammation model tissue LyC6(-) MFs are derived from LyC6(+) cells.

Temporal and spatial characterization of mononuclear phagocytes in circulating, lung alveolar and interstitial compartments in a mouse model of bleomycin-induced pulmonary injury

The mononuclear phagocyte system, including circulating monocytes and tissue resident macrophages, plays an important role in acute lung injury and fibrosis. The detailed dynamic changes of mononuclear phagocytes in the circulating, lung alveolar and interstitial compartments in bleomycin-induced pulmonary injury model have not been fully characterized. The present study was designed to address this issue and analyzed their relationships with pulmonary pathological evolution after bleomycin challenge. A total of 100 male C57BL/6 mice were randomly divided to receive bleomycin (2.5mg/kg, n=50) or normal saline (n=50) via oropharyngeal approach, and were sacrificed on days 1, 3, 7, 14 and 21. Circulating monocyte subsets, polarization state of bronchoalveolar lavage fluid (BALF)-derived alveolar macrophages (AMφ) and lung interstitial macrophages (IMφ, derived from enzymatically digested lung tissue) were analyzed by flow cytometry. There was a rapid expansion of circulating Ly6Chi monocytes which peaked on day 3, and its magnitude was positively associated with pulmonary inflammatory response. Moreover, an expansion of M2-like AMφ (F4/80+CD11c+CD206+) peaked on day 14, and was positively correlated with the magnitude of lung fibrosis. The polarization state of IMφ remained relatively stable in the early- and mid-stage after bleomycin challenge, expect for an increase of M2-like (F4/80+CD11c−CD206+) IMφ on day 21. These results support the notion that there is a Ly6Chi-monocyte-directed pulmonary AMφ alternative activation. Our result provides a dynamic view of mononuclear phagocyte change in three compartments after bleomycin challenge, which is relevant for designing new treatment strategies targeting mononuclear phagocytes in this model.

Receptors to interleukin-6 and adhesion molecules on circulating monocyte subsets in acute myocardial infarction

Purpose: Limited data are available on expression of receptors to adhesion molecules, a marker of endothelial cell activation, and cytokines by the three human monocyte subsets after MI. The interleukin-6 receptor (IL6r) has been implicated in the pathogenesis of atherosclerosis, a disease of inflammatory aetiology. We evaluated the dynamics of monocyte subset expression of receptors to vascular cell adhesion molecule (VCAM-1r), intercellular adhesion molecule (ICAM-1r), and IL6r after MI. Methods: Expression of VCAM-1r, ICAM-1r and IL6r was quantified by flow cytometry in patients with stable coronary artery disease (CAD,n=40) and on days 1, 3, 7 and 30 post ST-elevation MI (STEMI,n=50). Monocyte subsets were defined as CD14++CD16–(Mon1), CD14++CD16+(Mon2), CD14+CD16++(Mon3). Results: On day1 after STEMI, VCAM-1r expression was reduced on Mon1 (p=0.002), Mon2 (p=0.007), Mon3 (p=0.005). There was no change in monocyte ICAM-1r expression after MI, whilst its expression on Mon1 reduced by 30 days (p=0.001). IL6r expression was reduced on Mon2 after STEMI, with gradual upregulation on Mon1 and Mon2 during follow-up. View this table: Monocyte subset expression of receptors Conclusions: Circulating monocyte subsets involved in inflammatory responses appear to have reduced IL6r expression in the acute phase following STEMI. This may represent a regulatory feed-back mechanism aiming to re-balance the marked inflammation which is typically present after STEMI. There is also a decrease in VCAM-1r density on circulating monocytes after STEMI. This may reflect the selective homing of monocytes with high VCAM-1r expression to damaged myocardium.

165 SCAVENGER RECEPTORS MEDIATE UPTAKE OF MODIFIED LDL BY CIRCULATING BLOOD MONOCYTE SUBSETS: CONSEQUENCES FOR ATHEROSCLEROSIS.

A major risk factor for cardiovascular disease (CVD) is elevated LDL-cholesterol, which can undergo oxidative modification (mLDL). Experimental models show that mLDL in atherosclerotic prone vascular beds leads to increased...

Origin and function of the repair macrophage in the murine sterile wound

Experiments were performed to define the phenotype and origin of repair macrophages (mφ). Wound cells were isolated from 1 to 14 days following subcutaneous insertion of sterile polyvinyl alcohol sponges in mice and examined for monocyte/mφ markers by flow cytometry. F4/80+Ly6Chi cells with an inflammatory monocyte signature appeared early, followed by accumulation of F4/80+Ly6Clow/int repair‐like mφ. Ly6Chi wound monocytes expressed CD64 but not the mφ marker Mer tyrosine kinase (MerTK), similar to blood monocyte precursors. In contrast to blood monocytes, wound monocytes upregulated CD14 and had a proinflammatory cytokine production profile. F4/80+Ly6Clow/int mφ were CD64+MerTK+ and produced cytokines associated with repair including VEGF and TGF‐β. Examination of CX3CR1‐GFP mice and selective labeling of circulating monocyte subsets demonstrated that Ly6Chi monocytes preferentially migrated from the blood to the wound. Analysis of cells from adoptively transferred sponges suggested that Ly6Chi monocytes mature within the wound to become Ly6Clowmφ. Overall, these studies functionally and phenotypically distinguished wound monocyte/mφ subsets and identified MerTK as a potential marker for repair mφ during sterile inflammation. Research supported by R01 GM042859, K08 GM079227 and the RIH Department of Surgery.

Receptors to interleukin-6 and adhesion molecules on circulating monocyte subsets in acute myocardial infarction

The role of individual monocyte subsets in inflammation and recovery post-myocardial infarction (MI) is insufficiently understood. It was the objective of this study to evaluate the dynamics of monocyte expression of receptors to vascular cell adhesion molecule (VCAM-1r), intercellular adhesion molecule (ICAM-1r), and interleukin-6 (IL-6r) following MI and their relation to inflammatory cytokines, fibrinolytic factors and annexin V-binding microparticles. Expression of VCAM-1r, ICAM-1r, IL-6r on CD14++CD16-(Mon1), CD14++CD16+(Mon2), CD14+CD16++(Mon3) monocyte subsets were quantified by flow cytometry in patients with ST-elevation MI (STEMI, n=50), non-STEMI (n=48) and stable coronary artery disease (n=40). In STEMI, parameters were measured on days 1, 3, 7, 30. On admission with STEMI, VCAM-1r expression was reduced on Mon1 (p=0.007), Mon2 (p=0.036), Mon3 (p=0.005), whilst in NSTEMI there was significant up-regulation of expression by Mon2 (p=0.024) and Mon3 (p=0.049). VCAM-1r on Mon1 correlated positively with plasma IL-1β levels (p=0.001). IL-6r was reduced on Mon2 in acute STEMI, with upregulation of the receptor on Mon1 and Mon2 during follow-up. IL-6r density correlated negatively with plasma levels of tissue-type plasminogen activator (p=0.0005 for Mon1, p=0.001 for Mon2 and Mon3), and positively with annexin V-binding microparticles (p=0.03 for Mon1, p=0.005 for Mon2 and p=0.005 for Mon3). There was no change in monocyte ICAM-1r expression. In conclusion, expression of IL-6r and VCAM-1r is reduced on circulating monocyte subsets involved in inflammatory responses in STEMI. This may represent a regulatory feed-back mechanism aiming to re-balance the marked inflammation which is typically present following acute MI or selective homing of monocytes with high receptor expression to damaged myocardium.